ASA 124th Meeting New Orleans 1992 October

Previously, results were presented showing that varying the duration of a
distal vowel can produce assimilatory, rather than contrastive effects on
perception. In a /shwas/--/chwas/ series, a longer vowel yielded more /sh/
responses rather than more /ch/ responses. Varying /w/ duration produced the
standard contrast effect. The assimilative effect may reflect a chaining of
contrast effects: the long /a/ made the /w/ seem shorter, and the ``shorter''
/w/ made the initial segment seem longer. Alternatively, the lack of a distinct
acoustic boundary between /w/ and /a/ may have produced these results, in which
case results should be very different for a voiceless stop followed by a vowel.
In new experiments, a similar series was made ranging from /chkas/ to /shkas/,
and the /k/ and /a/ durations were varied separately. The /k/ produced the
usual contrast effect while the nonadjacent /a/ had no effect. These results
and their implications for the understanding of rate normalization will be
discussed. [Work supported by NIDCD Grant No. DC00219 to SUNY at Buffalo and an
NSF Graduate Fellowship to the first author.]